Circuit for amplitude modulation



Sept. 5, 19 50 BLOK ETAL 2,521,443

- CIRCUIT FOR AMPLITUDE MODULATION Fil e'd Oct. 12, 1948 IN VEN TORS JOHANNES MARINUS LODEVICUS JANSSEN LOURENS BLOK AGENT ,modulation"coniprises a ento'de 'in'whichfacar circuit-'arrangem t g ez d rib d -winj'i rier *Sig'nalis apb1ied' between" the control-grid 5;.y-ywhich the'fi i rr e circuit is dispense-dc i quencycarrier current which g I I I I Y 1 iow frequency n odulatingsi'gnais isdeveloped-un 551s de11VBd f1'0I n, a' load'=resi'stanceincluded inthe in the tw dfcircuits is constant; "ilhe rnodu latingw 20, twofurther electrodes through e resistance of c -v01tage=thus aCtsin' an epp "the1'Same i fv magnitude d wamd -iew-rr quency oltagema b I from the 'de'sired'modulated igh-frequenc'yvolt :30 age by supplying the voltage-taken iirom thel frequency signais siich a resonant circuit'has a 'high iiripedancefior quenc'y 'signals khutfa frequency orthe high-frequency oscillations- ''uringpurposes,"the filter oi the 'circuit will fre through acathode bias resistance 1 toflthe nega= case eacli'" new adjustmntof the frequency of? order toavoid alternating 'voitagea'cross there adjustment] of the tuned position This "im l i'e a-complication of the'control, if it sato becar ried outmanuall-y; or a complication 'of the de Usemight be'made of 'filters havin'g aiz rgeeband width; om-of a high-pass? filtenzsoethatztunin is'not -required. However,'iin.;this. caaiseith'ei;supe a The suppressor igrid'circuit furthermore includesvi' 21, 43 1,9 U 'EQR; e nEMQDeLAT eN Lonnie-3101 iahdffl hannes 'Mar inus Lodevicii's' Janssen; Emdhoven -Netherlands; assignoi'sto f- .HartfordiNationaFfiank and Trust Company, I

Hartford,; Conn.;Eastrustee F g i: V njat' bn otobifrla,194s; s 1No.'54,66 Q11. 71mm; Netherlands 0egoper144947" v, y cla m jixol. 3322-64), A

" r m e en me eenie-the filer-emcee n w foremblitude rnodulation.

\ quentlfexpensive. v I .7 4 K known' circuit-arrangement for an'iplitude The bj tu t invention is toqpr'ovide a new and the"cathddj aridral'in'odulatingfsignal is afpwith v g plied between theisuppres'srf-gridandthe cath-- Fbrgt his 'p'urpo 'ei the invention. -i aw od'e. This method of' modulation is referred .5120 circuit ai rangenfi'ent iri v'vhich a, high-fr en yf as "suppressor-grid modulation; I and it is based-on 5 carrier signal is i e w n the cdhtfolfgfldg '5' the action exerted by the'suppressor grid on'thefi' and "the" cath de fgg e t arg m currentdistributionbetwe'enctheanodeand the r and a'low-frequency' signal i app befw'nu screen-jg'rid,"-thisacti nbeing refrred to as the the'l athojdg andeaj w r griddont1-Q1]ing'. e curri'1t-distribution 7 central: "The highfrecurrenfl'distribution betwee t lfurthi if l gz. 5 moduiatedbythefl trodes. The modulated high-frequncvvoltage both the screen-grid circuit 'and the' anodee supply currentcircuit of either of the two further f' cuit inl uch inanner that,' to a nrst-approx1ma'-= electrodes; which circuit isconnected to -the' cath e high-f I ode. "The invention is characterized in that the ine instant latter electrode is connected tothe othei of the n frequency'currefitsfoccurrirrg at the high-frequency 'currents flowing' through theFtv'n sistance K r i Y circiiits. -A- niodulated high frequency voltage As-wiH- be seen hereinafter,- the"amp1itudeofw may be taken from a load resistan in'c u'ded in e the low frequency voltage 'occurringacross th'e 1 the anode circuit. However, in; hi arrangim m lo ad resistance is thus sosmaIL 'reIatiVeetQ"the hat 'ct-he a lowrfre mean -'amp1itude g f th e' flmodulated high-fre quency volta'ge occurringacross it, thatfdrther measures for suppressingthe unwanted lowfre-" quencyivoltage are not required orat 1east"mea's-" ures which'are easier and cheaper to'carr'y out are sufficient.-

"sistance to 'a filtr suitable for this ;purpose', for In order that theinvention'may'bemore clearly 5? hy-substituting 'f-o1"-"' 1';hedead resistanceincluded understood and readily carriedinto effect, itwill a paralle'lresonant-circuit now be'kdescribed morefully by reference' -to the the modu latedg-high fre V negligible, im pe'danc forarrangement according 'to' :the' invention}; the undesired low-frequency signals. H v 111i the;:circuit arran'gem nt' according 'to the Howeventhejuse 'ofpafil'ter-lor o ei tiine'd 11* invention ias-shownwinif'Fig-v2,- theJJcircui-t e1e--- cuit requires-additionalcomponent arts; fth mentsiusediin the same manner as those of'Fie.

' k v 1 aredesignated by identical reference numerals." adjustableism the case of gefie'ratorsvformeas- In Fig'.'2,' the:.eathode 2 of pentcde 'l is connected w que'ntly be 'constructed to' be'tunab1e'.- In" thisf'45 tiveiterm'inal of: a 'directvoltage source 9. "In

the high-frequencyosilhtionsIaIsbrequires'resistance T; itis shunted'by a'by-pass condenser"? I 8. The control-grid circuit comprises the high-"* frequency'alternating voltage" source II, which 0 sulip'lies-fthe voltage t dbe modulated. A negati v biasgv'oltage which is required for the adjust ment of the *c'urrent distributionzcontrol fis-fed tothe suppressortgr'id Why the voltage supply lOi vice ifwthe control liswcarriedvouta-aut'oi'naticall pression of, the; unwanted rrsienals-i is'iun'setisfacmfili a slow-frequency vVe,ltennating voltage supply; l2. v;

first intermediate electrode and the cathode.

3. A'circuit arrangement for producin amplitude modulation, comprising an electron discharge tube having in theorder named a cathode, a control grid, first and, second intermediary electrodes and an output electrode, means to apply a signal voltage to said control grid, means to apply a modulating voltage to said second intermediary electrode, a resistance load vi element of given value havin one end thereof connected to saidoutput electrode, means to connect a voltage source to the other end of said load element, and a second resistance element having a value substantially equal to said given value'interconnecting said output electrode and the said first intermediate electrode,

4. A circuit arrangement for producin amplitude modulation,'comprising an electron discharge tube'having inthe order named a cathode, a control grid, first and second intermediary electrodes and an output electrode, means to apply a signal voltage to said control grid, means to apply a modulating voltage to said second intermediary electrode, a resistance load element having one end thereof connected to said output electrode, means to connect a voltage source to .the other end of said load element, a second resistance element interconnecting said output electrode and the said first intermediate electrode, a bias resistance element connected to saidcathode, and a capacitor shunting Ss'aid bias resistance element, said capacitor having a low impedance value at the frequency of said signal voltage and a high impedance value at the irequency of said modulating voltage.

5. A circuit arrangement for producing ampli-' tude modulation, comprising an electron discharge tube having in the order named a cathode,'a controlgrid, firs't'and second intermediary electrodes and an output electrode, means to apply a signal voltage to said control grid, means said modulating voltage interconnecting the said i to apply a modulating voltage to said second in- 'termediary electrode to produce a modulating current flow in said first intermediate electrode "and said output electrode, a resistance load eleanode having a ratio relative to the said load resistance substantially equal to the ratio of'the modulating current in said. output electrode to ,the modulating current in said first intermediate electrode. 20

6. A circuit arrangement forproducing amplitude modulation, comprising an electron dis .charge tubehaving in the order named a cath-' ode, a control grid, a'screen grid, a suppressor grid and an anode, means to apply a signal voltage to said control grid, means to apply a modu-' lating voltage to said suppressor grid,,a resistance load element having one end/thereof con nected to saidanode, means to connect a voltage, source to the other end of said load ele- *ment,qand'a secondresistance element interconnecting said anode and the said screen grid.

LOURENS BLO'K. 1 JOI-IANNES MARINUS LODEVICUS JANSSEN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number! Name Date 2,224,690 Moodey et a1; Dec. 10, 1940 Wheeler Mar. 31, 1942 

